Nitroparaffins having 1-3 carbon atoms and mixtures thereof, and particularly nitromethane, are known to be sensitizers for water gel explosives. Some serious problems are encountered in producing stable water gel explosives using nitroparaffin sensitizers and those sensitized gels which are known are of generally low sensitivity and are usually detonated with the aid of boosters. Nitromethane is soluble to a degree, say up to 10%, in an aqueous phase. Higher concentrations of nitromethane can be used more effectively to sensitize a water gel explosive composition. To achieve the higher concentrations or a more sensitive condition, the insoluble portion of the nitromethane must be suspended or dispersed by mixing it as very fine droplets in the overall aqueous gel structure of the explosive composition. It is usually accepted that the finer droplets, the higher will be the sensitivity factor. In the case of the more fluid pourable and pumpable gels, the fine droplets of nitromethane have a tendency to coalesce into larger less effective droplets and to migrate until the insoluble nitromethane has effectively separated from the aqueous gel structure to form a separate layer. When this occurs, the overall composition becomes less sensitive and in most cases undetonable. This type of product is most unacceptable especially when the nitromethane sensitized explosive gel is poured or pumped through water which may cause the nitromethane to be separated from the aqueous gel structure more rapidly. Water attack on the aqueous gel structure accelerates this separation. Even stiff nonpourable or nonpumpable nitromethane sensitized gels show a tendency for the nitromethane to separate during storage.
In prior attempts to stabilize the nitromethane so that it resists coalescence and separation, various approaches have been taken. For instance, emulsifiers have been used for stabilizing the nitromethane, but the presence thereof appears to reduce the overall water resistance of such a composition. In storage, the separation shelf life of the emulsion-gel is directly related to the quality of the aqueous gel produced by the guar gelling agent, to the quality of the nitromethane emulsion as it is effected by the quality of the emulsifying agent, the size of the nitromethane dispersion and the mixing procedure.
Others have suggested the use of nitrocellulose as a gelling agent for the nitromethane but have failed to produce cap sensitive or higher sensitive compositions which indicates that high nitromethane concentrations or adequate dispersions were not even contemplated. In addition, a slower two-step process is taught for producing the composition wherein the nitroparaffin is first gelled after which it is combined by mixing with an aqueous oxidizer phase (Minnick, U.S. Pat. No. 3,419,444). This necessarily means that the nitromethane gel will be dispersed in a variety of particle sizes throughout the aqueous phase rather than in the more desirable smaller droplets.
Other attempts to inhibit nitromethane separation from aqueous gels include forming a nitromethane compound such as the Tris (hydroxymethyl) nitromethane which is soluble in the aqueous phase of the composition or by adding an alcohol to aid in making the nitroparaffin more soluble in aqueous gels (Minnick U.S. Pat. No. 3,419,444 and U.S. Pat. No. 3,409,485). However, once again booster systems are required to detonate these compositions and higher nitromethane concentrations are not contemplated.